Despite facing a wall of opposition, Cameron can be sure he has support from so-called 'Tory darling' Katharine Birbalsingh.

The former teacher was catapulted into the spotlight after being asked to speak at the Conservative Party Conference last year. Her outspoken manner and desire to speak the truth in the hope of exposing the failings of the current education system resulted in her suspension from school which she calls a case of "very bad judgement".

"I don't think I quite understood how big the conference would be", she says. "Had my school never sent me home, you never would have heard of me."

Birbalsingh, who was deputy head at St Michael and All Angels academy school in Camberwell, London, was given a standing ovation after her speech, but has since faced harsh criticism about her motives for telling the truth.

"A number of people attack me for my views. They say I'm doing this for my own benefit. But I’d like to know how I’ve benefitted from this. I’ve lost my job – a job a really loved. I’ve paid a massive price for telling the truth and I continue to tell the truth because I believe in it.

"The reason why I went into teaching was to change the world. And the way to change the world is through children. If we continue to deny our poorest an education, a chance to make something of our lives, then I don’t know how anyone can sleep at night knowing that’s what they’re doing.

But she admits it's a daily struggle to fight for what she believes in due to the reluctance of teachers to speak out.

"There are still a significant minority of people with a very loud voice who refuse to believe me. Teachers know it, but they don’t want it said. They’ll talk about it in the staff room but they’d never say it outside. They’re scared people would turn around and point the finger of blame at them.

"I’m accusing the system, not the teachers. They don’t want to ask for help for fear of it reflecting badly on them.

"Fear is strangling the system. Teachers can’t tell the truth. It smacks of a Stalinist Russia. It’s perfect just to be able to say I’m lying. Why would I lie? They say oh, she must want to be a politician, a media star, a talk show host. Am I? No. Why would I say it? The only explanation is I’ve invented all this in my head and I’m crazy and I’m making all these statistics up. We refused to accept the truth because it makes us feel bad."

Birbalsingh lays part of the blame at the door of the media.

"The public have a completely warped idea of what education is really like. I think some of them have a sense, but most have no idea of what’s going inside those schools. You imagine it’s like Grange Hill, Waterloo Road … But it’s just not."

But it is the idea of teachers not being able to speak out which really riles her.

"I'm not the only one who thinks the system isn't doing justice to our children but a lot of people say it behind closed doors. They’re scared. They say look at her – she told the truth and she lost her job. We’re not going to put our heads above the parapet.

"I’ve had numerous teachers emailing me, running up to me in the street, saying thank goodness someone said something. Then they say but I’m not going to tell you my name and then they run away again," she says. "They are drowning in silence."

"A number of people want to stick their heads in the sand and say we don’t have a problem. But all it does is perpetuate our class system and ensure our working classes cannot move forward, be well educated or have choices in life."

And here she makes a comment which surely must dispel the "Tory darling" label she has been trying hard to shrug off:

"The people who are closing these doors are those who had good education, were able to keep the doors open for themselves. And now they’re using that power to slam the door shut to those who don’t have a rich mummy and daddy or private tutors."

But surprisingly, Birbalsingh admits it is just another middle class idea where only those who can afford not to work can get involved.

"There’s no way you could set one up if you were working full time. The problem with the system is it’s taken up all my time. Anyone setting up a free school has sacrificed huge amounts of time and energy."

Eventually a chink in the armour of this seemingly unstoppable woman appears: "Maybe it won’t change people's lives- who knows? But at least it's something."